Implement `fullscreen' on Android 4.0 and later

* doc/emacs/android.texi (Android Windowing): Document what new
frame parameters are now supported.
* java/org/gnu/emacs/EmacsActivity.java (EmacsActivity): New
field `isFullscreen'.
(detachWindow, attachWindow): Sync fullscreen state.
(onWindowFocusChanged): Add more logging.
(onResume): Restore previous fullscreen state.
(syncFullscreen): New function.
* java/org/gnu/emacs/EmacsWindow.java (EmacsWindow)
(setFullscreen): New function.
* src/android.c (struct android_emacs_window): Add new method.
(android_init_emacs_window): Look up new method.
(android_set_fullscreen): New function.
* src/androidgui.h:
* src/androidterm.c (android_fullscreen_hook): Implement
accordingly.

2 files changed, 130 insertions, 3 deletions

diff --git a/java/org/gnu/emacs/EmacsActivity.java b/java/org/gnu/emacs/EmacsActivity.java
index 3156a144a0f..7e09e608984 100644
--- a/java/org/gnu/emacs/EmacsActivity.java
+++ b/java/org/gnu/emacs/EmacsActivity.java
@@ -26,12 +26,16 @@ import java.util.ArrayList;
 import android.app.Activity;
 import android.content.Context;
 import android.content.Intent;
-import android.os.Bundle;
 import android.os.Build;
+import android.os.Bundle;
 import android.util.Log;
-import android.widget.FrameLayout;
-import android.widget.FrameLayout.LayoutParams;
 import android.view.Menu;
+import android.view.View;
+import android.view.Window;
+import android.view.WindowInsets;
+import android.view.WindowInsetsController;
+import android.widget.FrameLayout.LayoutParams;
+import android.widget.FrameLayout;
 
 public class EmacsActivity extends Activity
   implements EmacsWindowAttachmentManager.WindowConsumer
@@ -56,6 +60,9 @@ public class EmacsActivity extends Activity
   /* Whether or not this activity is paused.  */
   private boolean isPaused;
 
+  /* Whether or not this activity is fullscreen.  */
+  private boolean isFullscreen;
+
   static
   {
     focusedActivities = new ArrayList<EmacsActivity> ();
@@ -104,6 +111,8 @@ public class EmacsActivity extends Activity
   public void
   detachWindow ()
   {
+    syncFullscreenWith (null);
+
     if (window == null)
       Log.w (TAG, "detachWindow called, but there is no window");
     else
@@ -131,6 +140,8 @@ public class EmacsActivity extends Activity
       throw new IllegalStateException ("trying to attach window when one"
                                        + " already exists");
 
+    syncFullscreenWith (child);
+
     /* Record and attach the view.  */
 
     window = child;
@@ -230,6 +241,9 @@ public class EmacsActivity extends Activity
   public void
   onWindowFocusChanged (boolean isFocused)
   {
+    Log.d (TAG, ("onWindowFocusChanged: "
+                 + (isFocused ? "YES" : "NO")));
+
     if (isFocused && !focusedActivities.contains (this))
       {
         focusedActivities.add (this);
@@ -257,6 +271,9 @@ public class EmacsActivity extends Activity
   {
     isPaused = false;
 
+    /* Update the window insets.  */
+    syncFullscreenWith (window);
+
     EmacsWindowAttachmentManager.MANAGER.noticeDeiconified (this);
     super.onResume ();
   }
@@ -279,4 +296,88 @@ public class EmacsActivity extends Activity
 
     super.onContextMenuClosed (menu);
   }
+
+  @SuppressWarnings ("deprecation")
+  public void
+  syncFullscreenWith (EmacsWindow emacsWindow)
+  {
+    WindowInsetsController controller;
+    Window window;
+    int behavior, flags;
+    View view;
+
+    if (emacsWindow != null)
+      isFullscreen = emacsWindow.fullscreen;
+    else
+      isFullscreen = false;
+
+    /* On Android 11 or later, use the window insets controller to
+       control whether or not the view is fullscreen.  */
+
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R)
+      {
+        window = getWindow ();
+
+        /* If there is no attached window, return immediately.  */
+        if (window == null)
+          return;
+
+        behavior = WindowInsetsController.BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE;
+        controller = window.getInsetsController ();
+        controller.setSystemBarsBehavior (behavior);
+
+        if (isFullscreen)
+          controller.hide (WindowInsets.Type.statusBars ()
+                           | WindowInsets.Type.navigationBars ());
+        else
+          controller.show (WindowInsets.Type.statusBars ()
+                           | WindowInsets.Type.navigationBars ());
+
+        return;
+      }
+
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN)
+      {
+        /* On Android 4.1 or later, use `setSystemUiVisibility'.  */
+
+        window = getWindow ();
+
+        if (window == null)
+          return;
+
+        view = window.getDecorView ();
+
+        if (isFullscreen)
+          {
+            if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT)
+              /* This flag means that Emacs will be full screen, but
+                 the system will cancel the full screen state upon
+                 switching to another program.  */
+              view.setSystemUiVisibility (View.SYSTEM_UI_FLAG_FULLSCREEN);
+            else
+              {
+                /* These flags means that Emacs will be full screen as
+                   long as the state flag is set.  */
+                flags = 0;
+                flags |= View.SYSTEM_UI_FLAG_FULLSCREEN;
+                flags |= View.SYSTEM_UI_FLAG_HIDE_NAVIGATION;
+                flags |= View.SYSTEM_UI_FLAG_IMMERSIVE;
+                flags |= View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY;
+                view.setSystemUiVisibility (flags);
+              }
+          }
+        else
+          view.setSystemUiVisibility (View.SYSTEM_UI_FLAG_VISIBLE);
+      }
+  }
+
+  @Override
+  public void
+  onAttachedToWindow ()
+  {
+    super.onAttachedToWindow ();
+
+    /* Update the window insets.  */
+    syncFullscreenWith (window);
+  }
 };
diff --git a/java/org/gnu/emacs/EmacsWindow.java b/java/org/gnu/emacs/EmacsWindow.java
index 0eca35cec61..90fc4c44198 100644
--- a/java/org/gnu/emacs/EmacsWindow.java
+++ b/java/org/gnu/emacs/EmacsWindow.java
@@ -128,6 +128,9 @@ public class EmacsWindow extends EmacsHandleObject
      events.  */
   public LinkedHashMap<Integer, String> eventStrings;
 
+  /* Whether or not this window is fullscreen.  */
+  public boolean fullscreen;
+
   public
   EmacsWindow (short handle, final EmacsWindow parent, int x, int y,
                int width, int height, boolean overrideRedirect)
@@ -1179,4 +1182,27 @@ public class EmacsWindow extends EmacsHandleObject
 
     return any;
   }
+
+  public void
+  setFullscreen (final boolean isFullscreen)
+  {
+    EmacsService.SERVICE.runOnUiThread (new Runnable () {
+        @Override
+        public void
+        run ()
+        {
+          EmacsActivity activity;
+          Object tem;
+
+          fullscreen = isFullscreen;
+          tem = getAttachedConsumer ();
+
+          if (tem != null)
+            {
+              activity = (EmacsActivity) getAttachedConsumer ();
+              activity.syncFullscreenWith (EmacsWindow.this);
+            }
+        }
+      });
+  }
 };